Mon Toan Bi quyet nam o sach bai tap

Meo lam bai thi DH:

(Tu van cua thay Nguyen Thuong Vo, cuu giao vien Toan, Truong THPT Ha Noi – Amsterdam).

Toi van noi voi HS, ra Ha Noi on thi, cac ban mat ba thu: tien bac, thoi gian va suc luc thi cac ban phai “moi” cho duoc ba thu: kien thuc co ban, cach trinh bay va toc do lam bai.

Kien thuc co ban o dau?

De dat diem cao, truoc het HS phai nam chac kien thuc co ban. Kien thuc co ban nam trong SGK va ba cuon sach bai tap Toan lop 10, 11, 12. Tai sao la sach bai tap Toan? La vi de thi

5 LUU Y TUONG NHU “VAT VANH” • Lam cau de truoc, cau kho sau. • Dau cong tru nhan chia phai het suc can than, ro rang. Can, logarit… nen viet ra dang sau, con so viet len dang truoc. Vi du, khi viet (can 2) nhan voi (3), chi can keo dai dau can mot chut thi se thanh (can cua 2) nhan (3). Vi vay nen viet 3 len truoc, thanh (3) nhan (can 2) thi ban co keo dau can dai bao nhieu cung khong so. • Dung nen ve hinh elip, hinh tron bang compa, de bi rach giay. Nen dung thuoc khoet lo tron va hinh elip. • Neu that thanh thao, hay su dung may tinh vao viec tinh nhung ham phuc tap. Co nhung nguoi tinh bang may xong lai phai tinh bang tay vi khong tin tuong vao ket qua, vua mat thoi gian vua gay uc che tam ly. • Dung dung hai thu muc, dung dung but xoa vi nhu vay co the bi coi la danh dau bai. Neu viet sai, cac ban hay gach di, viet lai.

DH co toi gan mot nua la kien thuc tu lop 11 va lop 10. Vi vay, neu khong co thay tong ket giup thi cu sach bai tap ma lam, lam tat ca bai tap trong do la da co the yen tam vao phong thi DH. Trong sach bai tap co ca dap so, lam xong co the doi chieu, tu tim ra cai sai. Bi nua, co the hoi cac thay giao o dia phuong, toi tin la cac thay deu co the giai thich duoc. Hai de thi nam 2003 ve tinh gia tri lon nhat - nho nhat, ra y het dang de trong SGK. De tich phan khoi B nam ngoai con de hon SGK nhung HS van khong lam duoc vi coi thuong SGK.

Dung tach ra luyen thi khoi A, khoi B, khoi D vi khong co su chenh lech ro ret ve do kho. De nam 2004, cau tich phan cua khoi B kho hon khoi A. Tat nhien, cung co nhung cau cua de khoi A ra kha hoc bua (nhu cau 5 duoc 1 diem cua nam ngoai) de tim HS gioi.

Bai lam: 6 - 8 mat giay la vua

Nhung tinh toan lat vat dung viet vao bai thi, hay tinh ra giay nhap. Mot bai thi chi 6 – 8 mat giay la vua, co nguoi lam den 12 mat giay thi qua la khung khiep. Troi nang nong, tim mai khong thay dap so de gay uc che cho nguoi cham bai. Vi du, sau khi tinh duoc tich phan, dung dinh nghia thay gia tri can tren can duoi, khi thay so vao co the lam ra giay nhap va dien ket qua vao, vi nguoi ta co the nham duoc, khong thay nao cham diem cho ban khi ban thay so vao ca. Hoac nhu khi giai phuong trinh bac hai cung khong can phai tinh ∆ luom thuom, dai dong trong giay thi. Neu khong nham duoc nghiem thi tinh ra giay nhap va dien ket qua. Khi ve ham so, can ve chinh xac, khong can dep.

Toi ki: sai co ban, lac de

Co nhung nguoi nho toi cham lai bai tren giay nhap, thay dung het nhung diem van thap. Do la vi khi lam bai tren giay nhap thi tap trung nhung khi chep ra bai thi, dau oc bat dau “long”, vi chu quan, nghi la lam xong roi. Tham chi vua chep vua nghi ra cach giai bai khac nen dong no danh dong kia, nham con so, vay la giay nhap dung con bai sai. Vi vay nen het suc chu y de tang toc do lam bai.

Mot dieu nua toi muon noi, do la cac ban dung xao dong vi nhung tin don, co nguoi gan ngay thi cu noi se ra de nay, ra de kia chi lam hoang mang tu tuong, chua bao gio toi thay cac tin don do la chinh xac ca. Tuan cuoi cung truoc khi thi, phai “quan triet”: khong hoc them, khong lam bai tap. Thay vao do, phai doc ky ly thuyet tu dau den cuoi.

Voi nguoi cham, cai “ky” nhat la sai co ban, sai co ban la gach ngay. Cai “ky” thu hai la lac de vi khong doc ky dau bai. Vi du, tiep tuyen tai diem khac voi tiep tuyen di qua. Tai diem chi co mot tiep tuyen, di qua co nhieu tiep tuyen. Neu khong doc ky de se rat nham. Sau khi phat de, dung cam dau lam ngay, hay doc ky de trong nam phut, gach duoi nhung y chinh, nhung tu quan trong trong de. Cau nao kho thi danh dau hoi (?) ra ben canh. De ra yeu cau tinh dien tich thi gach duoi tu “dien tich”, hoi khoang cach thi gach duoi tu “khoang cach”… de tranh nham.

Theo Sinh vien Viet Nam